(Meth)acrylic copolymer resin and coating film thereof

ABSTRACT

A coating resin that is thermoplastic, exhibits good appearance, solvent resistance and adherence and is excellent in abrasion resistance; and a coting liquid or coating film thereof. In particular, a (meth)acrylic copolymer resin (A) produced by radical polymerization of 4 to 50 mass % of (meth)acrylic acid (a-1), 0.5 to 17 mass % of (meth)acrylamide (a-2), and 35 to 95.5 mass % of a compound having reactive unsaturated bond other than the compounds (a-1) and (a-2). With respect to the coating film produced therefrom, both the glass transition temperature Tg1 measured by means of a rigid-body pendulum type viscoelasticity measuring instrument and the glass transition temperature Tg2 measured by means of a differential scanning calorimeter (DSC) are 110° C. or higher. The coating film is an abrasion resistant film whose abrasion resistance measured in accordance with the Taber abrasion testing method is 80 rotations or greater.

TECHNICAL FIELD

The present invention relates to (meth)acrylic copolymer resin and acoating film comprising the same, which is excellent in outwardappearance, solvent resistance and adhesion upon coating and drying onmetal and plastic materials of vehicles, automobile parts, homeappliances, instruments etc., and superior in wear resistance.

BACKGROUND ART

To prevent scratch and wear of metal and plastic materials of vehicles,automobile parts, home appliances, instruments etc., a method ofimproving durability against scratch and wear by applying and forming acoating film on such materials has been proposed. A coating film formedfor the purpose of preventing scratch and wear of such materials isclassified into crosslinked thermosetting resin and non-crosslinkedthermosetting resin, and the former crosslinked resin is often used fromthe viewpoint of wear resistance. Proposed methods of making thecrosslinked resin involve irradiation with UV or EB (JP-A 10-17689),applying heat energy (JP-A 11-181334) or reacting with isocyanate atroom temperature (JP-A 11-181334 and JP-A 2000-144049) to crosslinkresin with the curing agent. However, these methods often requireadditional UV or EB facilities or much heat energy for crosslinkingreaction and several hours for drying. Further, the crosslinked coatingfilm is problematic in treatment for disposal or in recycling etc.

Because of such problems in crosslinking and drying conditions forforming a coating film, a coating film of low-temperature-drying andnon-crosslinked thermoplastic resin is desired and proposed (JP-A7-156567), but does not realize performance such as sufficient wearresistance.

DISCLOSURE OF INVENTION

The object of the present invention is to provide a coating film (orfilm) ┌hereinafter we call coating film┘ comprising thermosettingcoating resin, particularly (meth)acrylic copolymer resin, which isexcellent in outward appearance, solvent resistance and adhesion and issuperior in wear resistance.

The present invention comprises the following constitution:

-   1. A wear-resistant coating film comprising (A) (meth)acrylic    copolymer resin, wherein the glass transition temperature (Tg1)    thereof as determined by a rigid pendulum viscoelastometer and the    glass transition temperature (Tg2) thereof as determined by a    differential scanning calorimeter (DSC) are 110° C. or more    respectively, and the wear resistance thereof as determined by a    Taber abrasion testing method is 80 times or more.-   2. The coating film according to claim 1, wherein the difference    among the glass transition temperature (Tg1) as determined by a    rigid pendulum viscoelastometer, the glass transition temperature    (Tg2) as determined by a differential scanning calorimeter (DSC) and    the glass transition temperature (Tg3) thereof calculated from a    monomer composition constituting the coating film is 30° C. or more.-   3. A (meth)acrylic copolymer (A) wherein the calculated glass    transition temperature (Tg3) thereof is 50 to 150° C.-   4. A (meth)acrylic copolymer resin (A) having a weight-average    molecular weight (Mw) of 20,000 or more, produced by radical    polymerizing (a-1) 4 to 50 wt % (meth)acrylic acid, (a-2) 0.5 to 17    wt % (meth)acrylic acidamide, and (b) 35 to 95.5 wt % compound    having a reactive unsaturated bond other than (a-1) and (a-2).-   5. A coating solution comprising the resin according to the    above-mentioned 4 dissolved in an organic solvent (B).

BEST MODE FOR CARRYING OUT THE INVENTION

The object of the present invention is to provide a thermoplasticcoating resin excellent in outward appearance, solvent resistance andadhesion and superior in wear resistance, as well as a coating solutionand coating film comprising the same.

The present inventors paid attention to the abrasive wear of(meth)acrylic copolymer resin, to examine improvements in wearresistance of its coating film. The present inventors paid attention tothe glass transition temperature of (meth)acrylic copolymer resin, thatis, the glass transition temperature (Tg1) as determined by a rigidpendulum viscoelastometer, the glass transition temperature (Tg2) asdetermined by a differential scanning calorimeter (DSC) and the glasstransition temperature (Tg3) calculated from a monomer compositionconstituting the coating film. As a result of extensive study, we foundthat when the glass transition temperature (Tg1, Tg2) as determined by arigid pendulum viscoelastometer and a differential scanning calorimeter(DSC) respectively are 110° C. or more, a wear-resistant coating filmhaving a wear resistance of 80 times or more as determined by a Taberabrasion testing method can be obtained, and further found that when thedifference between the glass transition temperature (Tg1, Tg2) asdetermined by a rigid pendulum viscoelastometer and a differentialscanning calorimeter (DSC) and the glass transition temperature (Tg3)calculated from a monomer composition constituting the coating film is30° C. or more, the (meth)acrylic copolymer resin is a coating filmexcellent in outward appearance, solvent resistance and adhesion andsuperior in wear resistance, and the present invention was therebycompleted.

Coating Film

The glass transition temperature (Tg1, Tg2) of the coating film, asdetermined by a rigid pendulum viscoelastometer and a differentialscanning calorimeter (DSC) in the present invention, is in the range of110 to 250° C., preferably 120 to 250° C., more preferably 130 to 250°C. When the glass transition temperature is less than 110° C., theformed coating film is poor in hardness and wear resistance, while whenthe glass transition temperature is higher than 250° C., the coatingfilm is hard and brittle and poor in hardness and abrasiveness.

The wear resistance of the coating film as determined by a Taberabrasion testing method in the present invention is 80 times or more,preferably 200 time or more.

The difference between the glass transition temperature (Tg1, Tg2) ofthe coating film as determined by a rigid pendulum viscoelastometer anda differential scanning calorimeter (DSC) and the glass transitiontemperature (Tg3) calculated from a monomer composition constituting thecoating film is 30° C. or more. When the difference is 30° C. or less,the coating film fails to exhibit sufficient wear resistance.

The calculated glass transition temperature (Tg3) of the (meth)acryliccopolymer (A) is in the range of 50 to 140° C., preferably 75 to 140°C., more preferably 100 to 140° C. When the glass transition temperature(Tg3) is less than 50° C., the coating film fails to exhibit sufficientwear resistance. When the glass transition temperature (Tg3) is higherthan 140° C., the coating film is rendered hard and brittle to lowerwear resistance adversely.

In the glass transition temperature (Tg1) determined by a rigid pendulumviscoelastometer, described in item 1 in the present invention, ameasuring device DDV-OPA III manufactured by A&D was used. In thismeasurement, a coating plate formed according to a method of forming acoating film was heated at a rate of 5° C./min. in a thermostaticchamber at 25° C. and then measured for its periodic change againsttemperature with a 6 mm pipe pendulum vibrated for an inherent period of0.6 second, to determine the rate of change, and its inflection pointwas expressed as the glass transition temperature Tg1 by this rigidpendulum viscoelasticity measuring method.

The glass transition temperature Tg2 determined by a differentialscanning calorimeter (DSC) described in item 1 in the present inventionwas determined by a measuring device DSC-60A manufactured by ShimadzuCorporation. In this measurement, 10 mg sample was accurately weighed,then subjected to pretreatment by heating at a rate of 30° C./min. from25° C. to 250° C. and then cooled at a rate of 10° C./min. from 250° C.to 25° C. After the pretreatment, the sample was heated as a standardsample at 10° C./min. with alumina, and the peak of thermal change wasexpressed as glass transition temperature Tg2.

The Taber abrasion testing method described in item 1 in the presentinvention was conducted according to an abrasion testing method (JISK5600-5-9) (ISO 7784-2: 1997). In the measurement method, the abrasiontest was carried out by a wear ring method (CS10F, loading 500 g)wherein the number of revolutions was read with naked eyes until thecoating film was shaved or the coating film was removed from a basematerial.

The glass transition temperature Tg3 calculated from a monomercomposition constituting the coating film described in item 2 in thepresent invention can be determined from a known method (Fox formula).The Fox formula is for calculating the Tg of copolymer from the Tg ofhomopolymer of each of monomers forming the copolymer, and is detailedin Bullet in of the American Physical Society, Series 2, Vol. 1, No. 3page 123 (1956)). The Tg of a compound having various reactiveunsaturated bonds as a basis for calculation of the Tg of copolymer bythe Fox formula can make use of numerical values described in Table 10-2(main starting monomers of coating acrylic resin) on pages 168–169 inShin Kobunshi Bunko (New Polymer Library), vol. 7, Introduction toSynthetic Resin for Coating (authored by Kyozo Kitaoka, KobunshiKankokai, Kyoto, 1974).

The thickness of the coating film is usually in the range of 1 to 50 μm,preferably 1 to 20 μm, more preferably 1 to 10 μm.

(A) (Meth)acrylic Copolymer Resin

Now, the (meth)acrylic copolymer resin (A) is described.

The (meth)acrylic copolymer resin (A) is a copolymer resin obtained byradical-polymerizing a composition consisting of (a-1) (meth)acrylicacid, (a-2) (meth)acrylic acid amide, and a reactive unsaturatedbond-containing compound (b) other than (a-1) and (a-2), wherein theweight ratio of (a-1)/(a-2)/(b) is (4to50)/(0.5to17)/(35to95.5). Thetotal amount of (a-1), (a-2) and (b) is 100 wt % (this applies here inafter). Preferably, the weight ratio of (a-1)/(a-2)/(b) is (10 to 40)/(3to 13)/(47 to 87). More preferably, the weight ratio of (a-1)/(a-2)/(b)is (20 to 30)/(5 to 10)/(60 to 75).

When the (meth)acrylic acid (a-1) is less than 4 wt %, the wearresistance of the coating film is deteriorated. On the other hand, whenthe (meth)acrylic acid (a-1) is higher than 50 wt %, the resultingcoating film is made hard and brittle thus failing to achieve desiredwear resistance. When the (meth)acrylic acid amide (a-2) is less than0.5 wt %, the wear resistance of the coating film is deteriorated. Onthe other hand, when the (meth)acrylic acid amide (a-2) is higher than17 wt %, the resulting coating film is made hard and brittle thusfailing to attain desired wear resistance. When the reactive unsaturatedbond-containing compound (b) other than (a-1) and (a-2) is less than 35wt %, the coating film is poor in film formability to cause defects inthe formed coating film. On the other hand, when the compound (b) ishigher than 95.5 wt %, the coating film is too soft and poor in wearresistance.

The weight-average molecular weight (Mw) of the (meth)acrylic copolymerresin (A) is in the range of 20,000 to 200,000, preferably 30,000 to100,000. When the Mw is less than 20,000, the coating film is renderedbrittle and poor in hardness and wear resistance, while when the Mw ishigher than 200,000, formation of the coating film is insufficient thusdeteriorating outward appearance in respect of gloss and turbidity.

The weight-average molecular weight (Mw) is determined by gel permeationchromatography (GPC) with polystyrene as standard.

The (meth)acrylic acid (a-1) in the present invention is acrylic acidand/or methacrylic acid.

The (meth)acrylic acidamide (a-2) in the present invention is acrylicacid amide and/or methacrylic acid amide.

The reactive unsaturated bond-containing compound (b) other than (a-1)and (a-2) contains (meth)acrylate as an essential ingredient andoptionally contains at least one compound selected from styrene, maleicanhydride, maleic acid, fumaric acid, itaconic acid and monoestersthereof.

The (meth)acrylic copolymer resin (A) maybe copolymerized with otherradical polymerizable monomers insofar as the calculated glasstransition temperature (Tg3) is in the range of 50 to 150° C.

The (meth)acrylic copolymer resin (A) can be obtained by copolymerizingthe (meth)acrylic acid (a-1), the (meth)acrylic acid amide (a-2) and thereactive unsaturated bond-containing compound (b) other than (a-1) and(a-2) in the presence of an initiator. The reactive unsaturatedbond-containing compound (b) used in the present invention includes, butis not limited to, (meth)acrylates such as methyl (meth)acrylate, ethyl(meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate,i-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl(meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate,cyclohexyl (meth)acrylate and benzyl (meth)acrylate, and compoundshaving nitrogen-containing reactive unsaturated bonds, such asN,N-dimethylaminoethyl (meth)acrylate, N, N-diethylaminoethyl (meth)acrylate and (meth) acrylonitrile, and the compounds having functionalgroup-containing reactive unsaturated bonds include compounds havinghydroxyl group-containing reactive unsaturated bonds, such as2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate,hydroxybutyl (meth)acrylate, polycaprolactone/hydroxyethyl(meth)acrylate adducts (Plaqucell F series (trade name) manufactured byDaicel Chemical Industries, Ltd.), polyethylene glycol/methacrylic acidadducts (Blenmer PE series (trade name) manufactured by Nippon Oil andFats Co., Ltd.) and polypropylene glycol/methacrylic acid adducts(Blenmer PP series (trade name) manufactured by Nippon Oil and Fats Co.,Ltd.), compounds having carboxyl group-containing reactive unsaturatedbonds, such as maleic acid, maleic anhydride, itaconic acid andmonoesters thereof, and compounds having glycidyl group-containingreactive unsaturated bonds, such as glycidyl (meth)acrylate,methylglycidyl (meth) acrylate, methylglycidyl (meth) acrylate andallylglycidyl (meth)acrylate. Styrene, α-methyl styrene, vinyl toluene,vinyl acetate, vinyl propionate, ethylene, propylene etc. are mentionedin addition to the (meth)acrylate monomers, and one or more of thesecompounds having reactive unsaturated bonds are used incopolymerization.

Solvent and Coating Solution

The solvent used in dissolving and dispersing the (meth)acryliccopolymer resin (A) in the present invention is not particularly limitedinsofar as the polymer is completely dissolved and removed byevaporation and two or more solvents may be mixed to attain preferableviscosity and evaporation rate for use in a coating solution and toprevent blushing of the coating film.

The organic solvent is preferably a mixture of solvent (c) dissolved inan arbitrary ratio in water and solvent (d) other than (c).

The solvent usable as the organic solvent (B) includes the solvent (c)dissolved in an arbitrary ratio in water, for example ether solventssuch as ethylene glycol monomethyl, ethylene glycol monoethyl, ethyleneglycol mono-n-propyl, ethylene glycol monoisopropyl and propylene glycolmonomethyl, as well as alcohol solvents such as methanol, ethanol,propanol, isopropanol and butanol. The solvent (d) other than (c)includes, for example, alkyl benzene solvents such as benzene, tolueneand xylene, acetate solvents such as ethyl acetate, propyl acetate,butyl acetate, amyl acetate, methyl acetoacetate, methyl Cellosolve andCellosolve acetate, and ketone solvents such as dioxane, acetone, methylethyl ketone, methyl isobutyl ketone and cyclohexanone.

To form the coating film, the (meth)acrylic copolymer resin (A) and theorganic solvent (B) in the present invention may be formed into acoating such that the solids content and viscosity of the coating areregulated according to an applicator and a coating method. The mixingratio of (A) to (B) by weight, that is, (A)/(B)), is (5 to 80)/(95 to20), preferably (10 to 70)/(90 to 30).

The radical polymerization initiator used in the acrylic copolymer resin(A) in the present invention includes organic peroxides such as benzoylperoxide, t-butylperoxy-2-ethyl hexanoate, t-butyl hydroperoxide, cumenehydroperoxide etc., azo compounds such as N,N-azobisisobutyronitrile,4,4-azobis(4-cyanopentanoic acid) etc. If necessary, a chain transferagent such as dodecyl mercaptan, mercaptoethanol, α-methyl styrene dimeretc. can be used.

The coating resin composition of the present invention can further beblended if necessary with pigments, an UV absorber, an antioxidant, aleveling agent and fine particles, and the resulting coating compositioncan be used not only as topcoat and interlayer coatings but also asclear coating and color coating.

Method of Producing the Coating Film

The acrylic copolymer resin (A) in the present invention can be appliedby each method onto a substrate etc. and dried by drying at roomtemperature to 110° C. for 20 seconds to form a coating film. Thesubstrate includes, for example, iron, aluminum, zinc, stainless steel,metallic materials obtained by subjecting the above materials to surfacetreatment, vinyl chloride, polyethylene terephthalate, polyethylene,polypropylene, polycarbonate, and plastic materials obtained bysubjecting the above materials to surface treatment. If necessary, thesebase materials can be coated with a primer, an interlayer coating and atop coating.

The coating resin of the present invention can be applied by a knowncoating method using spraying, brushing, a roller, dipping or a barcoater.

Method of Evaluating the Coating Film

The above diluted and regulated coating composition was applied by a barcoater to a thickness of 2 to 3 μm in terms of dry thickness onto a basematerial of polyvinyl chloride in a sheet form (thickness 1 mm×length100 mm×width 100 mm), and then dried in an atmosphere at 110° C. by ahot-air dryer for about 20 seconds to prepare each test specimen. Theresulting test specimen was observed and evaluated for the followingitems. The results are shown in Table 2.

State of the Coating Film

-   (1) Outward appearance-   {circle around (1)} Transparency: The coating film on the test    specimen thus prepared was observed with naked eyes, and evaluated    according to the following criteria.-   O: transparent-   Δ: slightly cloudy-   x: not transparent (opaque)-   {circle around (2)} Cracking: The prepared test specimen coating    film was observed with naked eyes, and evaluated according to the    following criteria.-   O: no cracking-   Δ: slight cracking-   x: cracking-   (2) Adhesion (crosscut adhesion): The prepared coating film on the    test specimen was observed in a crosscut adhesion test (K5400-8-5)    and evaluated in terms of number of remaining crosscuts/number of    crosscuts at the time of cutting.-   (3) Solvent resistance: The prepared coating film on the test    specimen was rubbed 50 times with a gauze impregnated with each    solvent (acetone/toluene) and evaluated according to the following    criteria:-   O: no trace-   Δ: slight trace-   x: evident trace or scratch    Physical Properties of the Coating Film-   (4) Wear resistance: The formed coating film on the test specimen    was examined by a wear ring method (CS10F, loading 500 g) in a Taber    abrasion testing method (JIS K5600-5-9), and the number of    revolutions was read with naked eyes until the coating film was    shaved or the coating film was removed from the base material.-   (5) Tg1, Tg2 of the coating film: The coating used in formation of    the test specimen was dried under conditions depending on the    following measuring devices, and measurements were recorded.-   {circle around (1)} Rigid pendulum viscoelastometer: DDV-OPA III    manufactured by A&D.-   {circle around (2)} DSC (differential scanning calorimeter): DSC-60A    manufactured by Shimadzu Corporation.

EXAMPLES

Here in after, the present invention is described in more detail byreference to the Examples and Comparative Examples, but the presentinvention is not limited to these examples.

Example 1

A 5-L four-necked flask equipped with a stirrer, a thermometer, anitrogen inlet tube and a reflux condenser was charged with 750 gisopropyl alcohol, 250 g toluene and 500 g methyl ethyl ketone, andwhile the flask was purged with nitrogen, the mixture was heated to 80°C. Just after heating, 100 g methacrylic acid, 40 g methacrylic acidamide, 502 g methyl methacrylate, 358 g isobutyl methacrylate and apolymerization initiator were continuously dropped into the mixture over5 hours with a constant delivery pump, and thereafter the polymerizationinitiator was further added thereto and the mixture was kept for 3 hoursto get methacrylic copolymer resin (A). Examples 2 to 8 and ComparativeExamples 1 to 6

Resin solutions were prepared in the same manner as in Example 1 exceptthat (meth)acrylic acid, (meth)acrylic acid amide, the compound having areactive unsaturated bond, and the solvent composition etc. were changedas shown in Tables 1-1 and 1-2. The results are shown in Tables 1-1 and1-2.

The resin solution obtained in each example was diluted and adjustedwith MEK to a solids content of 200%. Each coating resin product thusdiluted and regulated was applied by a bar coater to a thickness of 2 to3 μm (in terms of dry thickness) onto a substrate in a sheet form(thickness 1 mm×length·width 100 mm), and dried in an atmosphere at 110°C. by a hot-air dryer for about 20 seconds to form each test specimen.The resulting test specimen was evaluated for its coating film in therespective items. The results are shown in Tables 2-1 and 2-2.

Abbreviations are meant as follows: ST, styrene; MMA, methylmethacrylate; EA, ethyl acrylate; BA, butyl acrylate; nBMA,n-butylmethacrylate; iBMA, isobutyl methacrylate; 2-EHA, 2-ethylhexylacrylate; MAm, methacrylamide; MAc, methacrylic acid; AAc, acrylic acid;IPA, isopropanol; PM, propylene glycol monomethyl ether; TOL, toluene;and MEK, methyl ethyl ketone.

For Tg of compounds having various reactive unsaturated bonds usedherein in calculation, Table 10-2 (Main starting monomers of coatingacrylic resin) on pages 168–169 in Shin Kobunshi Bunko (New PolymerLibrary), Vol. 7, Introduction to Synthetic Resin for Coating (authoredby Kyozo Kitaoka, Kobunshi Kankokai, Kyoto, 1974) was used.

TABLE 1-1 Examples Used material: Theoretical Tg (° C.) of homopolymeris shown in Examples 1 to 8 parentheses. -1 -2 -3 -4 -5 -6 -7 -8 (A)(Meth) (a-1) (Meth) Mac (130) 100 200 250 60 400 200 200 acrylic acrylicacid Aac (106) 200 copolymer (a-2) (Meth) MAm (256) 40 60 80 10 10 60 60150 resin acrylic acid amide (b) Compound ST (100) 120 having a MMA(105) 502 515 400 808 400 515 515 532 reactive EA (-22) 25 70 25 25 118unsaturated nBA (-54) 122 bond nBMA (20) 358 200 200 200 iBMA (67) 2702EHA (-85) Total 1000 1000 1000 1000 1000 1000 1000 1000 Theoretical Tg3(° C.) 75.0 90.1 108.1 76.4 101.5 90.1 90.1 98.9 (B) (c) IPA 750 10001000 1000 1000 Solvent PM 1000 1000 1000 (d) TOL 250 MEK 500 500 500 500500 500 500 500 TOTAL 1500 1500 1500 1500 1500 1500 1500 1500 CoatingSolids 40 40 40 40 40 40 40 40 solution content (%) Molecular 4100066000 82000 43000 43000 58000 58000 58000 weight (Mw)

TABLE 1-2 Comparative Examples Used material: Theoretical Tg (° C.) ofhomopolymer is shown in Comparative Examples 1 to 5 parentheses. -1 -2-3 -4 -5 (A) (Meth) (a-1) (Meth) Mac (130) 20 100 510 100 acrylicacrylic acid Aac (106) copolymer (a-2) (Meth) MAm (256) 40 0 40 200resin acrylic acid amide (b) Compound ST (100) 200 656 having a MMA(105) 651 800 450 700 reactive EA (-22) 149 unsaturated nBA (-54) 200bond nBMA (20) iBMA (67) 2EHA (-85) 84 100 Total 1000 1000 1000 10001000 Theoretical Tg3 (° C.) 77.6 35.3 72.3 122.0 130.5 (B) (c) IPA 7501000 1000 1000 1000 Solvent PM (d) TOL 250 MEK 500 500 500 500 500 TOTAL1500 1500 1500 1500 1500 Coating Solids 40 40 40 40 — solution content(%) Molecular 47000 45000 31400 27500 — weight (Mw)

TABLE 2-1 Evaluation results of coating film Examples 1 to 8 EvaluationItem −1 −2 −3 −4 −5 −6 −7 −8 Glass theoretical  75 90 108  76 102 90 9099 transition Tg3 (° C.) temperature: Tg2 (° C.) by 130 150 165 120 150145 145 130 DSC Tg1 (° C.) by 175 205 210 115 155 195 195 135 rigidpendulum viscoelastometer Outward transparency ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯appearance: Cracking ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Adhesion: crosscut 95/100 100/100100/100 100/100 100/100 100/100 100/100 100/100 adhesion test SolventAcetone Δ ◯ ◯ ◯ ◯ ◯ ◯ ◯ resistance: Toluene ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Wear Taber200 300 400 200 300 400 350 400 resistance: abrasion test (CS10, 500 g,number of revolutions)

TABLE 2-2 Evaluation results of coating film Comparative Examples 1 to 5Evaluation Item −1 −2 −3 −4 −5 −6 Glass theoretical 78 35 72 122 131transition Tg3 (° C.) temperature: Tg2 (° C.) by DSC 85 45 110 duringduring film synthesis making Tg1 (° C.) by 85 50 105 cracking turbidrigid pendulum viscoelastometer Outward transparency X Δ ◯ ◯ notappearance: Cracking ◯ ◯ ◯ X measurable Adhesion: crosscut 80/100 80/10080/100 — adhesion test Solvent Acetone X X X — resistance: Toluene X X X— Wear Taber 10 20  20 — resistance: abrasion test (CS10, 500 g, numberof revolutions)

According to the results shown in Tables 2-1 and 2-2, the outwardappearance of the coating film was free of cracking, and the coatingfilm being excellent in solvent resistance and adhesion with performanceexcellent in wear resistance was obtained in the Examples. In theComparative Examples, on the other hand, the coating film was turbid orcracked, extremely poor in solvent resistance and wear resistance andevidently inferior to the coating film in the Examples.

INDUSTRIAL APPLICABILITY

For uses requiring durability against scratch and wear, the coating filmis applied preferably onto metal and plastic materials of vehicles,automobile parts, home appliances, instruments etc., and is superior inwear resistance thus preventing scratch and wear.

1. A wear-resistant coating film comprising (A) (meth)acrylic copolymerresin, wherein the glass transition temperature (Tg1) thereof asdetermined by a rigid pendulum viscoelastometer and the glass transitiontemperature (Tg2) thereof as determined by a differential scanningcalorimeter (DSC) are in the range of 110° C. to 250° C. respectively,and the wear resistance thereof as determined by a Taber abrasiontesting method is 80 times or more, wherein the difference between theglass transition temperature (Tg1) as determined by a rigid pendulumviscoelastometer and the glass transition temperature (Tg3) thereofcalculated from a monomer composition constituting the coating film is30° C. or more and wherein the difference between the glass transitiontemperature (Tg2) as determined by a differential scanning calorimeter(DSC) and the glass transition temperature (Tg3) thereof calculated froma monomer composition constituting the coating film is 30° C. or more,and wherein the (meth)acrylic copolymer resin (A) has a weight-averagemolecular weight (Mw) of 20,000 to 82,000, and is produced by radicalpolymerizing (a-1) 4 to 50 wt % of (meth)acrylic acid, (a-2) 0.5 to 17wt % of (meth)acrylic acid amide, and (b) 35 to 95.5 wt % of compoundhaving a reactive unsaturated bond other than (a-1) and (a-2), and the(meth)acrylic copolymer resin (A) is dissolved in an organic solvent(B).
 2. The wear-resistant coating film according to claim 1, whereinthe (meth)acrylic copolymer (A) has a calculated glass transitiontemperature (Tg3) of 50 to 150° C.
 3. The wear-resistant coating filmaccording to claim 1, wherein the (meth)acrylic copolymer (A) has acalculated glass transition temperature (Tg3) of 50 to 140° C.
 4. Thewear-resistant coating film according to claim 1, wherein the compoundhaving a reactive unsaturated bond other than (a-1) and (a-2) is atleast one compound selected from the group consisting of(meth)acrylates, compounds having nitrogen-containing reactiveunsaturated bonds, compounds having carboxyl group-containing reactiveunsaturated bonds, compounds having glycidyl group-containing reactiveunsaturated bonds, styrene, a-methyl styrene, vinyl toluene, vinylacetate, vinyl propionate, ethylene and propylene.
 5. The wear-resistantcoating film according to claim 1, wherein the organic solvent is amixture of solvent (c) dissolved in water and solvent (d) other than(c).
 6. A coating solution comprising a (meth)acrylic copolymer resin(A) dissolved in an organic solvent (B), said (meth)acrylic copolymerresin (A) having a weight-average molecular weight (Mw) of 20,000 ormore and being produced by radical Dolymerizing (a-1) 4 to 50 wt %(meth)acrylic acid, (a-2) 0.5 to 17 wt % (meth)acrylic acid amide. and(b) 35 to 95.5 wt % compound having a reactive unsaturated bond otherthan (a-1) and (a-2).
 7. The coating solution according to claim 6,wherein the compound having a reactive unsaturated bond other than (a-1)and (a-2) is at least one compound selected from the group consisting of(meth)acrylates, compounds having nitrogen-containing reactiveunsaturated bonds, compounds having carboxyl group-containing reactiveunsaturated bonds, compounds having glycidyl group-containing reactiveunsaturated bonds, styrene, α-methyl styrene, vinyl toluene, vinylacetate, vinyl propionate, ethylene and propylene.
 8. The coatingsolution according to claim 6, wherein the organic solvent is a mixtureof solvent (c) dissolved in water and solvent (d) other than (c).